An important substance in the preparation of fragrances in the musk field is 7-acetyl-1,1,3,4,4, 6-hexamethyltetralin. This substance has excellent odour and fixative properties. It is stable to alkali and light, soluble in most solvents, substantially colourless and persistent and is also relatively cheap. It is commonly prepared by acetylation of hexamethyltetralin in a Friedel-Crafts reaction. In turn, many routes have been proposed for the preparation of this latter substance. Several have been proposed involving the formation of an alicyclic attachment to substituted cymenes which in turn may be obtained from 8-hydroxycymene.
It is known from US 2 366 409 (Hercules) that 8-hydroxymenthene can be converted to a mixture of 8-hydroxycymene and 8-hydroxymenthane by means of a disproportionation reaction. This reaction appears to be a combination of hydrogenation and dehydrogenation ie. is a tranfer hydrogenation using 8-hydroxymenthene as hydrogen acceptor. For every molecule of 8-hydroxymenthene which is dehydrogenated, enough hydrogen is produced to hydrogenate two molecules of 8-hydroxymenthene. The Hercules reaction results therefore in an approximate 2:1 mixture of respectively 8-hydroxymenthane and 8-hydroxycymene.